Thank you so much for the answer!
Yes, I have added images.
I have tried 600x400 and it doesn't work still, the file type is JPEG(
Yes, I guess that is the reason of the problem.
But it is impossible to use 3.5 at this moment as my Russian technical support is planning to run this version in November.
Maybe are there other ways to set up images?((((
Thank you so much!